Screw compressor with sliding bearings

ABSTRACT

A screw compressor with sliding bearings includes a female rotor and a male rotor; a suction end-face of the male rotor and suction and exhaust end-faces of the female rotor are respectively provided with recessed holes, in which radial sliding bearings are arranged and matched with suction and exhaust side projecting shafts embedded; a thrust sliding bearing is arranged on an end-face of the suction side projecting shaft; passages are connected to the recessed holes are provided in the female and male rotors along the axis direction, and radial passages are provided to connect axial passages and rotor chamber. Using sliding bearings inside the rotors can simplify compressor structure and reduce occupied space and cost. Besides, the passages provided inside rotors simplify the liquid return structure of sliding bearings while cool the rotors, reduce the thermal deformation of the rotors, and improve the reliability and performance of the compressor.

BACKGROUND OF THE PRESENT INVENTION Field of Invention

The present invention relates to a field of screw compressors, and moreparticularly to a screw compressor with sliding bearings.

Description of Related Arts

The screw compressor generally has a body, a helical male and a femalerotor engaged with each other and arranged in parallel in the body,namely screw rotors. The male rotor and the female rotor need to besupported by the bearings mounted in the body, so that projecting shaftsare generally provided on both sides of the female and male rotors andfitted to the bearings.

Conventionally, there has been another screw compressor of the differentstructure. The screw compressor is not provided with projecting shaftson the end-faces of the female and male rotors to mount the bearing, butrecessed holes are drilled on the suction end-faces and the exhaustend-faces of the male rotor and the female rotor respectively. Therecessed holes are provided as bearing chambers and rolling bearings aredisposed in the bearing chambers to support the screw rotors. Forexample, Japanese patent JP-7-279868 disclosed a screw compressor havinga configuration in which projecting shafts at the suction side andexhaust side of the body enter the rolling bearings in the recessed holebearing chambers of the male rotor and the female rotor respectively.The male and female rotors are supported by these rolling bearings.

Screw compressors are widely used in various industrial sectors such asrefrigeration, power, chemical, machinery, etc., and have a high marketshare. However, the cost of screw compressors is high, which limits theexpansion of the market share of screw compressors. Screw compressorsgenerally use rolling bearings to support the screw rotors, but the costof the rolling bearing is high, and it is not suitable for a screwcompressor in which the bearing lubricant and injected medium into thecompressor are the same liquid. In addition, in the case of a screwcompressor where the screw rotor temperature is high, such as a watervapor screw compressor, the deformation of the screw rotor is large, andit is easy to cause the female and male rotors to be stuck. In order toprevent the female and male rotors from being stuck, a large meshingclearance and a large exhaust end-face clearance are generally provided,resulting in a decrease in the performance of the screw compressor.Therefore, it is necessary to reduce the temperature of the screw rotorand the deformation of the screw rotor, thereby increasing theperformance of the screw compressor.

SUMMARY OF THE PRESENT INVENTION

In order to reduce compressor production costs and solve the problem oflarge deformation of screw rotors on the condition of high exhausttemperature, the present invention provides a screw compressor withsliding bearings.

Accordingly, in order to accomplish the above objects, the presentinvention provides:

A screw compressor with sliding bearings, comprising: a body, screwrotors, and a sliding support structure for supporting the screw rotorsin the body, wherein recessed holes are provided on suction end-facesor/and exhaust end-faces of the screw rotors; the sliding supportstructure comprises radial sliding bearings which are arranged in therecessed holes and coaxially rotates with the screw rotors; or thesliding bearing structure has the recessed holes as bearing bushes ofthe radial sliding bearings; body projecting shafts fitted with theradial sliding bearings are arranged on the suction side or/and theexhaust side of the body, and the body projecting shafts and the radialsliding bearings form radial gaps at fitting positions; the radial gapsare connected to a lubricant inlet disposed on the body; passages areprovided inside the screw rotors, and rotor chamber between the screwrotors and the body is connected to the recessed holes through thepassages; lubricant enters the rotor chamber through the passages afterlubricating the radial sliding bearings.

Preferably, liquid supply grooves respectively are connected the radialgaps and the lubricant inlet are disposed on the projecting shafts ofthe body.

Preferably, the sliding support structure comprises a radial slidingbearing at suction side of the male rotor, a radial sliding bearing atsuction side of the female rotor and a sliding bearing at exhaust sideof the female rotor, wherein the recessed holes for fixing the radialsliding bearings are provided on the suction end-face of the male rotor,the suction end-face and the exhaust end-face of the female rotor, orthe suction end-face of the male rotor, the suction end-face and theexhaust end-face of the female rotor have the recessed holes as thebearing bushes of the radial sliding bearings; the body projectingshafts matching with the radial sliding bearings are respectivelyarranged on the suction side and the exhaust side of the body.

Preferably, the sliding support structure further comprises thrustsliding bearings (comprising a thrust sliding bearing at suction side ofthe male rotor and a thrust sliding bearing at suction side of thefemale rotor) disposed in the recessed holes on the suction end-faces ofthe screw rotors (comprising a female rotor and a male rotor), and thethrust sliding bearings match with thrust faces at bottoms of therecessed holes where the thrust sliding bearings are disposed; both thethrust faces and the thrust sliding bearings together bear axial forceof the screw rotors.

Preferably, the thrust sliding bearings are connected to end-faces ofthe corresponding body projecting shafts, or the thrust sliding bearingsare directly processed on the end-faces of the body projecting shafts.

Preferably, the passage comprises axial passages connected to thecorresponding recessed holes in the male rotor and the female rotor ofthe screw compressor, and radial passages disposed in the male rotor andthe female rotor of the screw compressor; wherein one end of the radialpassages is connected to the axial passages, and the other end of theradial passages is connected to the rotor chamber.

Preferably, the number of the radial passages is determined bylubrication and sealing requirements in the rotor chamber, and positionsof the radial passages towards the rotor chamber are determined by theinjection flow rate through the radial passages; the axial passages areconnected to bottoms of the recessed holes and extends along male andfemale rotor axes.

Preferably, the sliding support structure further comprises a radialsliding bearing, which matches with one end of the male rotor of thescrew compressor which extends out of the body, and is fixed to theexhaust side of the body.

Beneficial effects of the present invention are as follows.

The present invention simplifies the structure of the screw compressorand reduces the manufacturing cost of the screw compressor by providingthe radial sliding bearings in the recessed holes at the end-faces ofthe screw rotors or directly using the recessed holes as the bearingbushes of the radial sliding bearings. The present invention provides apassage structure in the screw rotors, which can be used as a coolingduct of the screw rotors, as a lubricant return passage of the slidingbearings, and as a injection pipe to the rotor chamber. The combinationof various functions such as cooling, lubrication, sealing and loweringnoise not only avoids the large meshing clearance and large exhaustend-face gap, but also improves the performance of the compressor.

Furthermore, the present invention provides the recessed holes on theend-faces of the male rotor and the female rotor, wherein the recessedholes are fitted with bearing bushes of the radial sliding bearings orare directly provided as the bearing bushes of the radial slidingbearings, and the projecting shaft on the suction side of the body isconnected with the thrust sliding bearings or the thrust slidingbearings are directly processed on the end-faces. As a result, norolling bearings are used to support the rotors, which simplifies thestructure of the compressor, improves the bearing capacity of thebearings, and reduces the space occupied by the compressor and the cost.Especially, the present invention is suitable for occasions where spaceis limited.

Furthermore, the present invention simplifies the liquid returnstructure of the sliding bearings by providing the axial and radialpassages in the male rotor and the female rotor as the return passagesof the sliding bearing lubricant. At the same time, the passages cancool the rotors, reduce the thermal deformation of the rotors, so as toprevent the rotors from being stuck in a given gap and improve thereliability of the screw compressor.

Furthermore, the radial passage provided in the male rotor and thefemale rotor of the present invention is equivalent to an injection pipeto the rotor chamber, which can cool the compression medium, lubricatethe rotors and seal the rotor chamber, so as to improve the performanceof the screw compressor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural diagram of a screw compressor using slidingbearings according to embodiment 1;

FIG. 2 is a structural diagram of a screw compressor using slidingbearings according to embodiment 2;

Element references: 1—suction end cap; 2—cylinder body; 3—radial slidingbearing at suction side of male rotor; 4—thrust sliding bearing atsuction side of male rotor; 5—male rotor; 6—exhaust end cap; 7—radialsliding bearing at exhaust side of male rotor; 8—seal; 9—female rotor;10—radial sliding bearing at exhaust side of female rotor; 11—radialpassage in rotors; 12—axial passage in rotors; 13—thrust face in rotors;14—thrust sliding bearing at suction side of female rotor; 15—radialsliding bearing at suction side of female rotor; 16—body axial passages;17—body radial passages; 18—liquid supply groove of sliding bearing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will be further described below in conjunctionwith the drawings and embodiments. The following embodiments areintended to illustrate the present invention instead of limiting it.

Embodiment 1

Referring to FIG. 1, a screw compressor comprises a body, screw rotors(comprising a female rotor 9 and a male rotor 5 arranged in parallel andengaged with each other), a radial sliding bearing at the suction sideof the male rotor 3, a thrust sliding bearing at the suction side of themale rotor 4, a radial sliding bearing at exhaust side of male rotor 7,a radial sliding bearing at the suction side of the female rotor 15, athrust sliding bearing at the suction side of the female rotor 14, and aradial sliding bearing at the exhaust side of the female rotor 10. Thebody comprises a cylinder body 2, and a suction end cap 1 and an exhaustend cap 6 which are respectively arranged at the suction side and theexhaust side, and connected to the cylinder body 2. A projecting shaftexists on the exhaust end-face of the male rotor 5 and extends out ofthe body. Recessed holes are provided at the suction end-face of themale rotor 5, the suction end-face and the exhaust end-face of thefemale rotor 9 to fix radial sliding bearings (i.e. the radial slidingbearing at the suction side of the male rotor 3, the radial slidingbearing at the suction side of the female rotor 15 and the radialsliding bearing at the exhaust side of the female rotor 10). A bodyprojecting shaft at suction side and a body projecting shaft at theexhaust side are provided on internal side faces of the suction end cap1 and the exhaust end cap 6 to match with radial sliding bearings incorresponding recessed holes, wherein the end-face of the bodyprojecting shaft at the suction side is provided with thrust slidingbearings (i.e. the thrust sliding bearing at the suction side of themale rotor 4 and the thrust sliding bearing at the suction side of thefemale rotor 14, which are not contacted with the radial sliding bearingin the same recessed hole) but match with the thrust face (i.e. thrustface in rotors 13) at bottoms of corresponding recessed holes. Axialpassages in rotors 12 connected to the recessed holes are providedinside the female rotor 9 and the male rotor 5 respectively along axialdirections, and radial passages in rotors 11 are provided in radialdirections, wherein the radial passages in rotors 11 is connected to theaxial passages in rotors 12 and extends to the rotor chamber.

The body projecting shafts are provided with liquid supply grooves ofsliding bearings 18, where body radial passages 17 are set in the bodyprojecting shafts. Body axial passages 16 are inwardly provided fromexternal faces of the suction end cap 1 and the exhaust end cap 6, andare connected to the body radial passages 17. The liquid supply groovesof sliding bearings 18, the body radial passages 17 and the body axialpassages 16 integrally all together serve as a lubricant supply line forthe sliding bearings. Clean, high-pressure and low-temperature lubricantenters corresponding radial sliding bearing clearances (i.e. radial gapsbetween bearing bushes and the body projecting shafts) through thesupply line. After lubricating the radial sliding bearings, part of thelubricant enters the rotor chamber through suction and exhaust end gapsof rotors, and the other part flows through the thrust sliding bearings(or directly) to enter the axial passages in rotors 12 and the radialpassages in rotors 11 through the thrust faces, and finally enters therotor chamber. All of the lubricant eventually is discharged out of thecompressor through the discharge port along with the compression medium.

The exhaust end cap 6 is provided with bearing chambers, and theprojecting shaft on the male rotor matches with the radial slidingbearing at the exhaust side of the male rotor 7 disposed in the bearingchamber. The bearing chamber is provided with a liquid inlet hole(lubricant inlet) for the lubricant to enter the bearing chamber of theradial sliding bearing at the exhaust side of the male rotor 7 throughthe liquid inlet hole, and to enter the gap of the radial slidingbearing through the gap between the seal 8 and the bearing bush of theradial sliding bearing at the exhaust side of the male rotor 7. Afterlubricating the radial sliding bearing, the lubricant enters the rotorchamber through the exhaust end gap of the male rotor or anotherpipeline.

Embodiment 2

Referring to FIG. 2, compared with the embodiment 1, a screw compressorof the embodiment 2 omits the radial sliding bearing at the suction sideof the male rotor 3, the thrust sliding bearing at the suction side ofthe male rotor 4, the radial sliding bearing at the exhaust side of thefemale rotor 10, the thrust sliding bearing at the suction side of thefemale rotor 14 and the radial sliding bearing at the suction side ofthe female rotor 15. In the embodiment 2, the recessed holes on thesuction end-faces of the female and male rotors directly serve asbearing bushes of the radial sliding bearings and match with the bodyprojecting shaft at the suction side. The thrust sliding bearing isdirectly processed on the end-faces of the body projecting shaft at thesuction side, which works with the bottom faces of the recessed holes(the thrust faces). The recessed hole on the exhaust end-face of thefemale rotor is also directly used as bearing bushes of the radialsliding bearing and match with the body projecting shaft at the exhaustside. In summary, the screw compressor disclosed in the presentinvention adopts the radial sliding bearings and the thrust slidingbearings in the female and male rotors, and does not need to use arolling bearing structure to support the rotors, which simplifies thestructure of the compressor and reduces space occupied by the compressorand cost. Especially, the present invention is suitable for occasionswhere space is limited. In addition, since the cooling and lubricationpassages (i.e. the axial passages and radial passages in rotors)connected to the lubrication passages of sliding bearings (i.e. thelubricant supply lines) is provided in the male rotor and the femalerotor, the liquid return structure of the sliding bearings is furthersimplified. At the same time, it can cool the rotor, reduce the thermaldeformation of the rotor, so as to prevent the rotor from being stuck ina given gap and improve the reliability of the screw compressor.Finally, the cooling lubrication passages in the male rotor and thefemale rotor are equivalent to increasing the injection passages to therotor chamber, and can cool the compression medium, lubricate the rotorsand seal the rotor chamber, so as to improve the performance of thescrew compressor.

The present invention is applicable to all screw compressors in whichthe bearing lubricant and the injection medium of the compressor are thesame liquid, such as oil-injected screw compressor, water-lubricatedscrew air compressor, water-lubricated steam screw compressor,refrigerant-lubricated refrigeration compressor, liquid process mediumcooled and lubricated process gas compressor, etc.

What is claimed is:
 1. A screw compressor with sliding bearings,comprising: a body, screw rotors, and a sliding support structure forsupporting the screw rotors in the body, wherein the sliding supportstructure comprises radial sliding bearings which are arranged inrecessed holes on suction end-faces or/and exhaust end-faces of thescrew rotors and coaxially rotate with the screw rotors; or the slidingbearing structure has the recessed holes, as bearing bushes of theradial sliding bearings, located on the suction end-faces or/and theexhaust end faces of the screw rotors; body projecting shafts fittedwith the radial sliding bearings are arranged on a suction side or/andan exhaust side of the body, and the body projecting shafts and theradial sliding bearings form radial gaps at fitting positions; theradial gaps are connected to a lubricant inlet disposed on the body;passages are provided inside the screw rotors, and a rotor chamberbetween the screw rotors and the body is connected to the recessed holesthrough the passages.
 2. The screw compressor, as recited in claim 1,wherein liquid supply grooves respectively connecting the radial gapsand the lubricant inlet are disposed on the projecting shafts of thebody.
 3. The screw compressor, as recited in claim 1, wherein thesliding support structure comprises a radial sliding bearing at asuction side of a male rotor (3), a radial sliding bearing at a suctionside of a female rotor (15) and a radial sliding bearing at an exhaustside of the female rotor (10), wherein the recessed holes for fixing theradial sliding bearings are provided on a suction end-face of the malerotor, a suction end-face and a exhaust end-face of the female rotor inthe screw compressor, or the suction end-face of the male rotor, thesuction end-face and the exhaust end-face of the female rotor have therecessed holes as the bearing bushes of the radial sliding bearings; thebody projecting shafts matching with the radial sliding bearings arerespectively arranged on the suction side and the exhaust side of thebody.
 4. The screw compressor, as recited in claim 1, wherein thesliding support structure further comprises thrust sliding bearingsdisposed in the recessed holes on the suction end-faces of the screwrotors, and the thrust sliding bearings match with thrust faces atbottoms of the recessed holes where the thrust sliding bearings aredisposed.
 5. The screw compressor, as recited in claim 4, wherein thethrust sliding bearings are connected to end-faces of the correspondingbody projecting shafts, or the thrust sliding bearings are directlyprocessed on the end-faces of the body projecting shafts.
 6. The screwcompressor, as recited in claim 1, wherein the passage comprises axialpassages connected to the corresponding recessed holes in a male rotorand a female rotor of the screw compressor, and radial passages disposedin the male rotor and the female rotor of the screw compressor; whereinone end of the radial passages is connected to the axial passages, andthe other end of the radial passages is connected to the rotor chamber.7. The screw compressor, as recited in claim 6, wherein a number of theradial passages is determined by lubrication and sealing requirements inthe rotor chamber, and positions of the radial passages towards therotor chamber are determined by a injection flow rate through the radialpassages; the axial passages are connected to bottoms of the recessedholes and extend along axes.
 8. The screw compressor, as recited inclaim 1, wherein the sliding support structure further comprises aradial sliding bearing, which matches with one end of a male rotor ofthe screw compressor which extends out of the body, and is fixed to theexhaust side of the body.